1. Field of the Invention
This invention relates to the field of grain aeration. More particularly, the invention is concerned with an apparatus for grain aeration to effect cooling, conditioning (e.g., partial drying) or fumigating grain stored in upright bins. In preferred forms, the invention provides grain aeration apparatus including upright, opposed, tubular perforate air inlet and outlets ducts within a grain bin with a fan assembly for forcing air through the inlet duct, transversely through the stored grain within the bin, and then upwardly through the outlet duct.
2. Description of the Prior Art
The standard grain aeration systems either push or pull air through the height of the grain using a fan located at the base of the grain bin, the top of the grain bin or a combination of fans on both top and bottom of the grain bin. Because the air must traverse the entire height of the grain mass, resistance to airflow is great, and large fans that consume large amounts of electrical power must be used to achieve acceptably large airflow. An alternative apparatus places two semi-circular, perforated, corrugated, metal ducts vertically on the sides of the bin to move air through grain stored in the bin horizontally instead of vertically. However, installation of the semi-circular ducts on the walls is costly and the weight of the grain causes damage to the corrugated ducts as grain is withdrawn from the silo. A hole, near the bottom of the grain bin is still required for the installation of the aeration fan and/or duct.
A 1985 publication by K. F. Loo entitled Silo Storage in Malaysia, Proceedings of International Seminar held at Kuala Lampur, Malaysia, Oct. 9-11 (1985) describes a grain aeration system comprising perforated air inlet and outlet ducts with axial fans coupled to the ducts. However, this reference makes use of identically sized (10 hp) fans.
Another reference Aeration of Grain in Commercial Storages published by the U.S. Department of Agriculture discloses an aeration system with opposed perforate ducts, that makes use of only a single exhaust fan.
The present invention solves the problems mentioned above and provides a distinct advance in the state of the art. In particular, the apparatus for aeration of grain hereof is efficient and economical to install, operate and maintain.
The preferred grain aeration apparatus of the present invention is operated in combination with a grain bin. The grain aeration apparatus includes inlet and outlet ducts positioned adjacent the inside face of the grain bin wall and extending along at least a portion of the height thereof. The duct walls are preferably smooth and un-corrugated, with ports distributed along a portion of their length. An inlet fan is attached to the inlet duct""s upper end. The inlet fan forces aeration air through the inlet duct, out the inlet ports and into grain stored in the bin. An outlet fan is attached to the upper end of the outlet duct. The outlet fan pulls air from the outlet duct and thereby pulls aeration air from grain stored in the bin through the outlet ports. The outlet fan is relatively larger than the inlet fan in terms of air-moving capacity in order to move more air than is supplied by the inlet fan. Thus air is pulled from the grain surface in a separate airpath than the duct-to-duct flow, in order to cool or condition the grain above the level of the perforations.
In preferred forms, the inlet and outlet duct are formed from synthetic resin pipe. The duct walls are imperforate for a distance of 1.5 to 1.9 bin diameters below the top of the grain bin, after which the ports consist of between 6 and 8% of the remaining duct surface area. Each pipe section is approximately 20 feet long, and requires only two attachment brackets per section. The preferred outlet fan is relatively larger than the inlet fan and both fans are positioned on top of the grain bin. Furthermore, it is preferred that the outlet duct be positioned in proximity to the area within the grain bin where the grain height is the greatest. This is done in order to keep air from xe2x80x9cshort-circuitingxe2x80x9d within the bin.
In alternate embodiments, the aeration system of the invention includes level sensor(s) located within the grain bin and operable to determine the level of grain therein, and particularly whether or not the level of grain in the bin is above the level of the duct ports.